The present invention relates to a cleaning apparatus used in particular for cleaning electronic components.
This type of apparatus is used in the electronics industry, particularly downstream of a wave soldering apparatus where electronic components are soldered on printed circuit boards.
In order to obtain a good soldered joint, in a soldering apparatus, the boards are first coated with flux, then they undergo a pre-heating stage where the volatile components of the flux evaporate and where the boards are pre-heated, the boards then pass along a standing wave of liquid solder, which they lick with their lower face whereafter the said boards exit from the soldering apparatus.
At that time, the boards carry many traces of more or less decomposed flux residues which have to be removed by the cleaning apparatus.
In typical manner, cleaning is achieved by spraying a solvent both over and under the boards carried by a conveyor going through the enclosure of the cleaning apparatus.
There are of course several spraying stages in the successive cleaning operations, typically four in number: pre-washing, washing, rinsing and final rinsing.
The solvent used in the final rinse-spraying stage is drawn by a final rinsing pump from a reservoir of purified solvent. After spraying, the solvent drains off into a second reservoir wherefrom it is drawn by a rinsing pump and sent back into the rinse-spraying ramps. The solvent used in the rinsing stage drains off into the second reservoir. Part of said solvent is routed via an overflow into a third reservoir shared by the washing stage and by the prewashing stage. It is drawn from that third reservoir by a pump which delivers it into the wash and prewash spraying ramps. After spraying, the solvent, by then containing more and more impurities, is routed towards the third reservoir.
Part of the solvent flows through an overflow from said third reservoir towards a draining reservoir. And because of the high cost of the solvents used, these are purified by an annexed distillation installation which draws the solvent filled with impurities from the draining reservoir and returns it once purified to the reservoir of the final rinse stage.
In order to prevent any considerable increase of impurities concentration in the successive stages, it is important to operate with large quantities of solvent which are constantly recycled and of which only a small part is progressively conveyed to the draining reservoir.
It is also known to have ultrasonic cleaning installations, but which generally use static solvent baths in which a batch of printed circuit boards is immersed for a preset period of time, this being done successively in several baths. This type of installation is not really suitable for automation and in particular for the continuous conveying of printed circuit cards from the inlet to the outlet of the cleaning apparatus.
There are also installations where the cleaning is performed exclusively with ultrasounds, and if, for various reasons, certain series of boards have to be spray-cleaned, then it is necessary to have another installation to this end, hence incurring a duplication of installations, an increased space requirement, and increased costs, maintenance, etc.